1. Field of the Invention
The present invention relates to magnetically recording information. More particularly, this invention relates to an information processing device, such as a camera that magnetically records information onto a magnetic recording part of a film.
2. Description of Related Art
Cameras are known that use a film with a magnetic recording part. Such a camera typically has two perforation detectors that detect perforations in the film. A frequency of recording and a timing for commencement of magnetic recording are determined based upon a perforation detection signal from the first perforation detector. A timing for termination of magnetic recording and a timing for termination of feeding the film are determined based upon a perforation detection signal from the second perforation detector. See, for example, published unexamined Japanese patent application Hei 4 (1992) - 328536.
FIG. 7 indicates a relationship between a position of a photo-interrupter and a magnetic head of a conventional camera capable of magnetic recording. FIG. 7 shows a film 100 with a magnetic recording part used in the camera, wherein the film 100 is positioned facing the camera aperture.
In addition, the camera is of the so-called normal wind type. In a normal wind type camera, frames of film are withdrawn from the film cartridge and exposed one by one. After all of the frames have been exposed, the film is then wound back into the film cartridge.
A film advance spool (not shown) is provided on the left side of FIG. 7. It is assumed that a film cartridge chamber (not shown) exists on the right side of FIG. 7. Therefore, the film 100 advances in a direction to the left of FIG. 7, and rewinds in a direction to the right of FIG. 7. Also, the leader of the film 100 (not shown) is on the left side of FIG. 7.
On one side of the film 100, two perforations are provided for each photographic frame. One of the two perforations PX is located on the advance spool side of any photographic frame Fn (n=1, 2, . . . ). The other of the two perforations PY is located on the film cartridge chamber side of the photographic frame Fn.
Emulsion is applied on one surface of the film 100 for image recording, and a magnetic recording medium is applied on the other surface of the film 100 for magnetic recording. A magnetic recording area Rn (n=1, 2, . . . ) is thereby established for each photographic frame Fn.
The camera has a perforation detection circuit with two photo-interrupters (not shown). Detection position 101 of the first photo-interrupter and detection position 102 of the second photo-interrupter are established as shown in FIG. 7 so that the position 101 is closer than the position 102 to the film cartridge chamber, and the position 102 is closer than the position 101 to the advance spool. In addition, a magnetic head 103 is established at a position nearer to the advance spool than to the film cartridge chamber, as shown in FIG. 7.
Borders CX and CY separate the photographic frame Fn from adjacent frames Fn-1 and Fn+1. The border CX is located on a side of the photographic frame Fn adjacent the advance spool, and the border CY is located on a side of the photographic frame Fn adjacent the film cartridge chamber.
For any photographic frame Fn, the perforation PX has an edge XF nearest the advance spool and an edge XR nearest the film cartridge chamber. Additionally, the perforation PY has an edge YF nearest the advance spool and an edge YR nearest the film cartridge chamber.
FIG. 7 shows distances L1 through L7. L1 is the distance between the borders CX and CY separating the film frames. L2 is the distance from the edge YF of the perforation PY of the photographic frame Fn-1 to the edge XR of the perforation PX of the photographic frame Fn. When the photographic frame Fn is at the specified photographic position, L3 is the distance between the detection position 101 and the edge YR of the perforation PY.
L4 is the distance between the recording center of the magnetic head 103 and the border CX. L5 is the distance from a) an end of the magnetic recording range Rn nearest to the advance spool, to b) the border CX. L6 is the length of the magnetic recording range Rn of each photographic frame Fn measured from a) the edge of the magnetic recording range Rn nearest to the advance spool, to b) the edge of the magnetic recording range Rn nearest to the film cartridge chamber. L7 is the distance between the edge of the magnetic recording range Rn nearest to the film cartridge chamber and the border CY.
The magnetic recording operation of a conventional camera capable of magnetic recording will now be described with reference to FIG. 8.
When the edge XR of the perforation PX of any photographic frame Fn (n=1, 2, . . . ) is at the detection position 102 of the second photo-interrupter, the frame is in a specified photographic position. The frame is photographically exposed while in the specified photographic position.
FIG. 8 (a) shows photographic frame Fn in the specified photographic position. After exposure of the frame Fn is completed, advancement of the film 100 commences.
As shown in FIG. 8 (b), the edge YF of the perforation PY passes the detection position 101 of the first photo-interrupter as the film 100 is advanced.
After the edge YF has passed the detection position 101, the film 100 continues to advance and the edge YR of the perforation PY passes the detection position 101. See FIG. 8 (c).
A timer determines the length of time between the time the edge YF passes the detection position 101 and the time the edge YR passes the detection position 101. The speed of the film advancement is then determined based upon the length of time determined by the timer and the distance between the edges YF and YR of the perforation PY. The frequency of magnetic recording is then determined according to the determined film advancement speed so that the specified density of magnetic recording can be obtained. Subsequently, the magnetic head 103 commences magnetic recording.
Next, when the edge YF of the perforation PY passes the detection position 102 of the second photo-interrupter as shown in FIG. 8 (d), the magnetic head 103 ceases magnetic recording, and the film advancement motor commences reducing the film advancement speed to zero.
When the edge XR of the perforation PX of the next photographic frame Fn+1 is at the detection position 102 of the second photo-interrupter as shown in FIG. 8 (e), advancement of the film 100 is terminated, and frame Fn+1 is in the specified photographic position.
However, problems exist with the conventional camera capable of magnetic recording as described above. First, the film advancement speed is unstable during periods of time after a photographic frame has been exposed and before the next photographic frame is in position for exposure.
Specifically, the film advancement speed is unstable as the film 100 is accelerated to a stable advancement velocity after taking a picture, and again as the film 100 is decelerated to zero velocity to complete the advancement. During these time periods magnetic recording is not performed because the speed of the film advancement is not constant.
As a result, the effective magnetic recording area for each photographic frame is shortened by the length of magnetic recording area that passes by the magnetic head 103 while the film 100 is either accelerating or decelerating.
In addition, with a conventional camera capable of magnetic recording, two perforation detectors are used to control magnetic recording on the film 100 and to control advancement of the film 100. Thus, mounting space for both perforation detectors must be provided. Other cost-related considerations also exist.